The pup was born smaller and weaker than his siblings - but with an awesome glow in the dark coat

But let's hope his incredibly rare glow in the dark coat can give him the strength of The Incredible Hulk.

The pup - a breed of hound - left dog breeders baffled when he emerged last week.

A male and female were born with startling green fur.

The female died but the male has survived - although he is very weak.

"I couldn't believe it when I first saw them," Aida Vallelado Molina told The Local.

"I thought the puppies were dirty and tried to clean them, but the colour wouldn't come off," said Molina, who breeds dogs with her father in the town of Laguna de Duero, near Valladolid in Spain.

The surviving male is now beginning to lose his pigment.

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A pair of Spanish dog breeders were shocked recently when two pups were born green.

The cause of the death of the dead puppy, and the reason for its odd colouring, are now being investigated by local vet Daniel Valverde.

"There are no other recorded cases of this happening in Spanish scientific literature," he told local newspaper Laguna al Día after contacting Madrid's Complutense University.

Valverde is now carrying out virological and bacteriological tests to try and find an answer.

Examples of green puppies have been reported before.

In 2012, the Daily Mail reported a Labrador pup born with a green hue who was named 'The Hulk'.

His owners said research suggested it was the result of exposure to a substance called biliverdin, which can be found in the placenta.

A puppy was also reported to have been born with green fur at an animal shelter in New Orleans in 2008.

An animal welfare expert said it is a rare condition.

"Sometimes, when a puppy is born, the amniotic fluid mixes with the placenta and dyes the coat of the puppy and it almost always happens to very light colored puppies. There are not health concerns - it's really just a discoloration in the birthing process," said Anna Zorrilla from Louisiana SPCA.